Method Reserve

cpp/src/arrow/io/memory.cc:113–128

}

Status BufferOutputStream::Reserve(int64_t nbytes) {
  // Always overallocate by doubling.  It seems that it is a better growth
  // strategy, at least for memory_benchmark.cc.
  // This may be because it helps match the allocator's allocation buckets
  // more exactly.  Or perhaps it hits a sweet spot in jemalloc.
  int64_t new_capacity = std::max(kBufferMinimumSize, capacity_);
  while (new_capacity < position_ + nbytes) {
    new_capacity = new_capacity * 2;
  }
  if (new_capacity > capacity_) {
    RETURN_NOT_OK(buffer_->Resize(new_capacity));
    capacity_ = new_capacity;
    mutable_data_ = buffer_->mutable_data();
  }
  return Status::OK();
}

// ----------------------------------------------------------------------
// OutputStream that doesn't write anything